I see that Google Webmasters give me some numbers as impressions, and of course, I know impression literal meaning. But can anyone please explain what impressions are in the context of Search Engine? How they are measured and why some advertisement agents like buysellads.com use them for ads prices?

2 Answers
2

The number of times pages from your site were viewed in search results, and the percentage increase/decrease in the daily average impressions compared to the previous period. (The number of days per period defaults to 30, but you can change it at any time.)

Can you point out exactly where Buyselladds is mentioning impressions in their case? Because I think they're talking about impressions of the ads they're serving and not what you're looking at in Webmaster Tools. The general concept is the same eg. how many times did people see your ad, but the two numbers wouldn't have any actual relation between them.

So, what if your page appear in 10th SERP, but people change their keywords without seeing it? Does it increase your impressions?
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Saeed NeamatiJul 15 '11 at 17:56

+1 for thinking along the same lines as me :)
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John Conde♦Jul 15 '11 at 17:58

3

@saeed, it will increase your position if the new search phrase they use causes your site to again appear in the search results. Basically, any time your site appears in someones search results it is an impression.
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John Conde♦Jul 15 '11 at 17:59

Impressions: The number of times pages from your site were viewed in
search results, and the percentage increase/decrease in the daily
average impressions compared to the previous period. (The number of
days per period defaults to 30, but you can change it at any time.)
(source)

In advertising it has a similar but different meaning.

Impression : According to the "Basic Advertising Measures," from FAST
, an ad industry group, an impression is "The count of a delivered
basic advertising unit from an ad distribution point." Impressions are
how most Web advertising is sold and the cost is quoted in terms of
the cost per thousand impressions (CPM). (source)